Valvuloplasty Catheter And Methods

ABSTRACT

A valvuloplasty catheter has a dog-bone shaped balloon with semi-compliant smaller diameter waist and non-compliant larger diameter bulbous end regions. The balloon centers across the valve with the waist adjacent to the annulus. One bulbous region serves to hyperextend the valve leaflets and the other assists in stabilizing the balloon position to reduce migration. The semi-compliant waist increases in diameter as fluid enters the balloon until it comes into contact with the valve annulus. The pressure within the balloon per unit of volume delivery has a greater slope after contact with the annulus than before resulting in a change in slope for the pressure versus volume curve. The diameter of the balloon and annulus are determined at this inflection point when the balloon contacts the annulus.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/104,636 filed Oct. 10, 2008 entitled Valvuloplasty Catheter AndMethods, U.S. Provisional Application Ser. No. 61/112,566 filed Nov. 7,2008 entitled Valvuloplasty Catheter And Methods, and U.S. ProvisionalApplication Ser. No. 61/145,705 filed Jan. 19, 2009 entitledValvuloplasty Catheter And Methods, all of which are hereby incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates to percutaneous transcatheter and transapicalcardiac valve implantation. More specifically, this invention relates toa device to better dilate the aortic valve leaflets than prior art andassess aortic valve annulus.

BACKGROUND OF THE INVENTION

Calcific aortic stenosis is a common cause of acquired valvular heartdisease with substantial morbidity and mortality. Its incidenceincreases exponentially in older patient populations. Fibrosis,degeneration and subsequent calcification are no longer believed to bepassive or purely degenerative in nature, but in fact are predominantlyactive processes mediated by underlying cellular mechanisms. Over time,as fibrosis and calcification worsens, valve leaflets becomeincreasingly rigid, restricting their ability to open. This, in turn,impedes the antegrade flow of blood through the heart resulting inseveral clinical syndromes including progressive heart failure. Othercauses of deformed and stenotic aortic valvular lesions includerheumatic heart disease, as well as nonacquired (i.e. congenital) heartdisease. Initial stages of stenotic valvular heart conditions are welltolerated by the patient, but when leaflet restriction becomes severe,invasive measures such as aortic valve replacement have commonly beenrequired.

With the advent of catheter-based cardiovascular procedures, minimallyinvasive balloon valvuloplasty techniques were developed to dilatestenosed valves, such as calcific, rheumatic and congenitally stenosedleaflets. During this procedure, a catheter having a deflated balloon ispercutaneously inserted into a vein or artery and advanced until theballoon is positioned within the heart valve needing treatment. Theballoon is then inflated to dilate the diseased valve opening,disrupting the rigid sheets of calcium and thereby permitting enhancedleaflet mobility. Balloon dilation, depending on the disease process,may result not only in the development of numerous flexible hinge pointswithin fibrosed and calcified leaflets, but also separation of fusedcommissures. After the leaflets have been dilated, the balloon isdeflated and removed from the patient's cardiovascular system.

Ideally, an infinite number of “hinge pointes” should be createdcircumferentially along the inner margin of the aortic valve annulus,from which the rigidly calcified leaflets arise. Retention of inflexiblecalcified ledges extending into the valve leaflets can prevent symmetricexpansion and incomplete apposition of implanted stent valves againstthe annulus. This, in turn, may result in both peri and central valvularinsufficiency of an inadequately deployed percutaneous stent-valve.Aggressive attempts to predilate with an oversized balloon can becomplicated by an annular tear or rupture, resulting in potentiallycatastrophic and generally fatal complications. Predilatation withundersized balloons may avoid this complication but render the valve illprepared for treatment.

In many current instances, valvuloplasty is performed with polymericballoon catheters that can achieve relatively high pressures at a fixeddiameter. Balloons made of non-distensible plastic materials areexpanded using fluid pressure up to a certain diameter after which,increases in fluid pressure within the balloon produce very littlechange in balloon diameter. These balloons can achieve high pressuresfor an effective therapy, but have several inherent limitations.

For example, it is difficult to expand these balloons, and then returnthem to their pre-expansion configuration. The pre-expansion profile ofthese balloons can be somewhat reduced by prefolding during themanufacturing process. However, once inflated, the folded balloonsegments are expanded within the vascular system. When deflated forremoval, these segments arrange to a flattened state with a much largerprofile, often called “winging”. Withdrawal of these balloons thereforerequires larger vascular introductory sheaths and thereby increases therisk of trauma to the vessels, resulting in compromised blood flow to anextremity or post operative bleeding. Additionally, non-distensibleballoons also have thick cones—transitions from the cylindrical diameterto the catheter shaft diameter. These regions of the balloon make thecatheter stiff, thereby increasing the risk of vascular trauma andincreasing the difficulty of advancing through tortuous peripheralarterial anatomy.

Since the radial dimensions of the catheter balloon must greatlyincrease when inflated to achieve aortic valve dilation, a highlyelastic material such as latex can be used to construct the balloon.Distensible balloons use these elastic materials and generally haveexcellent initial profiles and improved flexibility for introduction andtravel through the vascular system. In addition, they possess gooddeflated profiles for removal from the vascular system. However, thesehighly elastic materials have significant limitations. For example, itmay be difficult to control the expansion diameter of these balloons.The elastic materials continue to expand in diameter as pressureincreases and therefore have no inherent limit on maximal diameter aswith non-distensible balloons. Thus, distensible balloons can be unsafefor valvuloplasty, as the elastic limit can easily be exceeded when theballoon is fully inflated, potentially causing the balloon to rupturewithin the patient. Additionally, the balloon diameters can become toolarge for the valve being dilated causing rupture and tearing of boththe valve and its adjacent structures.

In addition, prior art catheter balloons have been associated withmechanical injury to the cardiac chambers. For example, tissue near theventricular apex may be injured due to the forceful longitudinalmovement of the inflated balloon across the valve and within the cardiacchamber. In another example, sudden and unexpected movements of theballoon can cause further tissue damage. Blood and the vascular wallsurface are inherently slippery against common catheter balloons whichcan result in significant balloon migration. As inflation fluid (e.g.,contrast media) is introduced, the catheter balloon enlarges andeventually assumes a cylindrical or axial ovoid shape. This shapecreates a tendency for the balloon to suddenly and uncontrollably pop inand out of the valve site and migrate deep into the left ventricle. Insome situations, this sudden balloon movement following inflation canincrease the difficulty to position the balloon accurately within thevalve leaflets, cause tissue damage and even catastrophic puncturing ofthe left ventricle.

Further, typical catheter balloon shapes tend to completely obstruct theflow of blood through the heart while inflated. Without perfusionthrough or around the catheter, the catheter balloon inflation time isbelieve to be limited to a few seconds before risking complications dueto profound hypotension.

A further disadvantage of prior art valvuloplasty balloons is itsfrequent failure to restore adequate flexibility to the aortic valveleaflets. That is, mere dilation with these previous balloon designs maynot be enough to adequately open the severely fibrosed and calcifiedleaflets. The prior art balloon catheters are cylindrical in shape whenfully inflated and thus have their maximal inflated diameter limited bythe narrower sinotubular ridge and valve annulus at the distal andproximal margins respectively of the aortic root sinuses. Efforts toexpand beyond these limits can result in tearing of the aortic valveannulus, catastrophic aortic insufficiency or rupture of the aorticroot. In addition, traditional balloon catheter methods generally resultin eventual restenosis of the aortic valve leaflets in 6-18 months,negating some or all of the regained flexibility.

Examples of some of these prior art catheter designs, as well as otherrelated catheter designs are discussed and disclosed in the followingU.S. Pat. Nos. 4,327,736; 4,777,951; 4,787,388; 4,878,495; 4,819,751;4,909,252; 4,986,830; 5,352,199; and 5,947,924 and U.S. Pat. PublicationNo. 2005/0090846; the contents of all of which are incorporated byreference.

What is needed is a balloon valvuloplasty catheter that overcomes all ofthese disadvantages of the prior art. Indeed, what is needed is aninvention that not only overcomes the disadvantages of the prior art intreating calcific aortic stenosis but also aortic stenosis resultingfrom congenitally abnormal valves and/or rheumatically injured valves.

SUMMARY OF THE INVENTION

One embodiment according to the present invention is directed to adog-bone-shaped balloon catheter for performing valvuloplasty on astenotic aortic or pulmonary valve or for opening up any stenoticconstriction within a tubular member of the body. The tubular membercould be, for example, any blood vessel of the body including a coronaryartery, peripheral artery, veins of the body, esophagus, trachea,intestinal vessels, bile ducts, ureter, and the like. This embodimenthas additional utility for use in predilatation of the aortic valveleaflets prior to placing a percutaneous aortic valve or otherprosthetic device used for aortic valve repair, replacement, or implant.This embodiment may also be formed with a larger or smaller diameterballoon and used in arteries, veins, body orifices, or other holloworgans of the human body where dilatation along with a diametermeasurement are needed. It provides advantages over the standardcylindrically-shaped valvuloplasty balloon due to the dog-bone shape forthe balloon as well as the construction of the balloon.

Generally, the dog-bone shape allows the bulbous portions of the balloonto self-center on each side of the aortic annulus and position thenarrower diameter waist adjacent to the annulus. The larger bulbousproximal end region of the balloon is positioned into contact with theaortic valve leaflets such that inflation of the balloon pushes theleaflets outward against the aortic sinus. The bulbous proximal portionof the balloon allows the aortic valve leaflets to be cracked or brokenat or near their base and hyperextended outwards toward the sinus in amanner that provides greater benefit than that provided by a standardcylindrical balloon without the concern for dissecting the annulus. Thenarrow waist of the dog-bone balloon is formed such that the smallerdiameter waist will not dissect the narrower annulus region. The distalbulbous region, which is located in the left ventricular outflow tract(LVOT), helps to prevent the balloon from migrating downstream duringinflation due to blood pressure generated from the beating heart.

The dog-bone-shaped balloon of the present invention is preferablyformed with a semi-compliant material in the smaller diameter waistregion and with a non-compliant material for the proximal and distalbulbous end regions. The waist region functions to more accuratelymeasure the diameter of the annulus than what can be attained usingstandard echocardiographic measurements. The waist also serves tomeasure the compliance characteristics of the annulus and thereby helpsthe physician to perform the valve dilatation procedure with a greaterdegree of safety to the patient against possible annular dissection.Inaccuracies with the standard echo measurements exist due in part tothe anatomically oval shape of the annulus which results in typicallyundersized estimates for the diameter of the annulus. Such undersizingoften can lead to incorrect sizing of the percutaneous valve andresultant poor valve function. The semi-compliant waist of the presentinvention is able to firmly contact the oval waist, readjust its shape,and provide a more accurate measurement of its true diameter whileensuring that the annulus is not exposed to dilating forces that couldcause annular dissection.

The semi-compliant waist preferably has an equilibrium diameter atapprox 0.1-0.2 atm of internal pressure that is smaller in diameter thanthe annulus diameter; the bulbous proximal and distal end regions aresized to make full contact with the valve leaflets and the LVOT,respectively. Thus as the balloon is initially inflated across theannulus, it tends to self-center with the bulbous regions on each sideof the annulus. As fluid is further injected into the balloon, theinternal balloon pressure increases as the diameter of the waistincreases in accordance with the compliance curve defined by thesemi-compliant waist material and method of construction. When theinternal balloon pressure reaches approx 2 atm, the leaflets of a vastmajority of patients will have been pushed outwards against the aorticsinus by the proximal bulbous region. At a pressure of approx 2 atm thedistal bulbous balloon region lodges in the LVOT upstream of the annulusand any anatomical obstructions found in the LVOT are pushed outward bythis bulbous portion. The waist enlarges in diameter and defines the lowend of the annulus diameter for which this balloon is intended to beused.

Further injection of fluid volume into the balloon can occur until theballoon waist enlarges further and comes into contact with the annulus.The relative volume that has been injected into the balloon has beencontinuously monitored by measuring the movement of a syringe plunger ofan inflation device. The internal pressure within the balloon ismonitored via a pressure transducer located within the balloon andmeasures an inflection in the rate of pressure increase per change involume injected into the balloon. At this inflection point the slope ofchange in pressure versus change in volume curve changes to a steeperslope that is reflective of the compliance of the annulus plus theballoon waist. The pressure at this inflection point corresponds to thediameter of the waist and therefore measures the diameter of theannulus. Although the waist may come into full contact with the annulus,it does not provide an outward force that could contribute to annulardissection since the resilient, elastic, semi-compliant waist resiststhe approx. 2 atm of internal balloon pressure.

It is noted that the inflection point or change in slope of the pressureversus volume curve may be enhanced by making the bulbous portions ofthe balloon non-compliant. Thus as fluid is injected following contactof the waist with the annulus, these bulbous end regions cannot increasein volume and hence it is the compliance of the annulus and waist thatis being observed.

Further injection of fluid into the balloon can further provideadditional outward force in the proximal bulbous region to push theleaflets outward at an even higher force up to 3 or 4 atm or possiblyhigher. The curve of the change in pressure versus change in volumeinjected continues to follow a slope indicative of the annulus plus thewaist. The forces pushing outwards against the annulus however remainlower than the internal balloon pressure. For example, if contact of thewaist with the annulus was made at 2 atm, then an internal pressure of 3atm will apply a force of only 1 atm against the annulus, thus providingthis embodiment with a safety against causing annular dissection. Thepresent invention has the ability to apply pressure onto the annulus ina more controlled manner due to the restraining force provided by thesemicompliant waist. This applied pressure that is placed onto theannulus is available to the physician following waist contact with theannulus as identified by the presence of the inflection point. The slopeof the pressure versus volume curve following contact of the waist withthe annulus also allows the physician to assess the strength andstiffness of the annulus.

Other methods are possible for measuring the waist diameter and hencethe annulus diameter at the inflection point. In one method the balloonis inflated with contrast fluid that is visible under x-ray fluoroscopy;also radiopaque markers placed on the balloon can be visualized byfluoroscopy. As the balloon comes into contact with the annulus asidentified by an inflection point as described earlier, fluoroscopy isused to measure the diameter of the waist and hence indicate thediameter of the annulus. In another method a piezoelectric material knowin the industry for measuring tension is placed around at least aportion of the waist circumference. Stretching this piezoelectricmaterial to a greater extent will result in a proportional electricalsignal that is indicative of the diameter of the waist. At theinflection point, the electrical signal would reflect the diameter ofthe waist and hence the annulus diameter.

An alternate method for measuring waist diameter can be accomplished byplacing an electrically resistive material around at least a portion ofthe circumference of the waist. Expansion of the waist will result in achange in resistance that is indicative of the waist diameter. Othermeans such as capacitive or inductively coupled sensors can be placedalong a portion of a circumferential path around the balloon waist.These sensors are capable of detecting distances or separation from onesensor to another and can be used to identify the waist diameter at theinflection point. An ultrasound sensor can also be place within theinterior of the balloon and used to sense the edges of the balloon oredges or perimeter of the annulus when the waist comes into contact withthe annulus. Such intravascular ultrasound technology is currently beingused in the industry for measuring diameters of coronary and peripheralblood vessel and can be located on the guidewire shaft that extendsthrough the center of the balloon.

In one embodiment, the inflation tool used to inject fluid into thedog-bone-shaped balloon catheter of the present invention is adisposable, hand operated, syringe-like device. The tool is fluidlyconnected to the balloon catheter and also electrically connected viawire or RF signal to a pressure transducer or other sensor such as thosepreviously described located in or on the balloon or within the cathetershaft near the balloon. A variable resistor or other means is used todetect a change in movement of the syringe plunger with respect to thesyringe barrel. Since the inflation tool is hand operated, variabilitycan occur in the rate of delivery of fluid to the balloon catheter. Anadditional pressure transducer may be located within the syringe barrelto account for inertial and compliance effects that could alter theaccuracy of the balloon pressure and volume delivery measurement duringthe inflation of the balloon. A display located on the inflation toolindicates the balloon pressure, the pressure when the waist contacts theannulus, and the diameter of the waist and hence the annulus diameter atthe inflection point.

The inflation tool is able to deliver the initial approximately 90-98%of the fluid volume to fill the balloon to an equilibrium volume andshape at a low internal balloon pressure of approx 0.1-0.2 atm in approx1-5 seconds. The second portion of the balloon filling is performed overthe next 1-5 seconds to allow for a more controlled and steady deliveryof fluid to the balloon and a greater ability of observing theinflection point as indicative of a change in slope of the pressureversus volume delivery curve. The inflation tool has two plungers thatallow the balloon to fill rapidly to an equilibrium size to shorten thetime that the balloon is being inflated and depriving the patient fromblood flow through his LVOT. The plungers also restrict the flow frombeing delivered too rapidly when the inflection point is being observed.One plunger has a one-way valve to allow the fluid to be rapidly removedfrom the balloon following the inflation period.

Several methods are described for forming a balloon having asemi-compliant waist and non-compliant bulbous end regions. In oneembodiment a semi-compliant dog-bone balloon is formed with a resilientor elastic material such as polyurethane or other thermoplasticelastomeric polymer. The waist can be supported using a braid, axialfibers, or slotted material to prevent the waist from extending axiallyduring the expansion of the balloon. The bulbous end regions are furthersupported by applying a non-compliant material such as polyethyleneterephthalate (PET) to the outside or within the bulbous end regions toreduce volume expansion of these regions. In another embodimentcoextrusions of semi-compliant and non-compliant materials are alsodescribed as part of a potential method for forming the dog-bone-shapedballoons. Several other methods for forming the balloon arecontemplated.

Additional embodiments of dog-bone and non-dog-bone shaped balloons arealso possible. These embodiments offer some advantages over the standardcylindrical balloon currently used for valvuloplasty but may have somedisadvantages over the preferred embodiment having a semi-compliantwaist and non-compliant bulbous regions.

Additional embodiments include a balloon formed entirely from anon-compliant material or entirely a semi-compliant material and havinga dog-bone shape are possible and are expected to have improvedpositioning characteristics across the annulus and ability tohyperextend the aortic valve leaflets compared to standard cylindricalballoons. The non-compliant balloon generally will not have the abilityto measure the diameter of the annulus via pressure sensing withoutapplying the entire internal balloon pressure to the annulus. Thesemi-compliant balloon generally will not have a sharp inflection pointdue to the ability of the bulbous end regions to grow in volume as fluidis injected thereby not causing an abrupt change in the slope of thepressure versus volume curve. Also as one continued to increase theinternal balloon pressure to attain contact of the waist with theannulus to measure the annulus diameter, the bulbous proximal end regioncould be growing in size in an uncontrolled manner resulting inpotential dissection in the sinus region.

A further embodiment is directed to a dog-bone-shaped balloon with anon-compliant waist and semi-compliant end regions. This balloonprovides for improved positioning across the annulus over a standardcylindrical balloon but is unable to provide a measurement via pressuremeasurement for the annular diameter in a manner described for thesemi-compliant waist. The bulbous regions may be exposed to varyingpressure increments to hyperextend the aortic valve leaflets to anextent that is appropriate to a specific patient as identified underfluoroscopy.

Yet a further embodiment is a valvuloplasty balloon catheter that iscomprised of two separate balloons one contained inside of the otherballoon. The inner balloon is a smaller balloon that has a relativelyabrupt profile such that it can locate well in the pocket that istypically found just upstream of the aortic valve annulus. This smallerinner balloon is inflated initially to position the balloon catheterproperly across the annulus. Immediately after the catheter ispositioned, the second larger outer balloon is inflated to cause theproximal aspect of the outer balloon to push the leaflets outwardsagainst the wall of the sinus. The distal portion of the outer ballooncan be of variable length and can be cylindrical in shape. The proximaland distal aspects of the outer balloon can also form a dog-bone shapeand can take on the characteristics of any of the dog-bone embodimentsdescribed in this disclosure including being formed from semi-compliantand non-compliant materials.

An additional embodiment for a valvuloplasty balloon has the feature ofproviding perfusion to the patient while the balloon is inflated. Duringinflation within the LVOT, standard balloons block blood flow to thehead and other organs of the body. To mitigate this concern, thestandard balloons are inflated for only approx 10-15 seconds while thepatient is undergoing rapid pacing to temporarily reduce his leftventricular pumping output. A perfusion balloon allows the dilation ofthe aortic valve leaflets to occur over a period of minutes instead ofseconds and would obviate the need for rapid pacing. A perfusion balloonmay be used to more effectively deliver drugs that could help maintainnative valvular function and reduce valvular restenosis. Other methodssuch as using cryotechnology or ultrasound may be more effectivelyadministered to the patient in order to treat the plaque or calciumbuildup that occurs in patients with aortic valve stenosis inconjunction with the perfusion balloon.

The perfusion balloon of the present invention has multiple smallballoons, approximately five, that are arranged such that they toucheach other and form a circle. The balloon can be bonded to each otheralong the lines with which they make contact. Inflation fluid ismanifolded into each of the five balloons on the proximal end and thedistal ends of each of the balloons is blocked off. The central regionbetween the five balloons is used to provide a passage for blood flow.The support for this structure is derived from the contact of oneballoon to the next. The internal blood flow perfusion area for atypically sized aortic valve would be approximately 0.4 cm squared.

In another embodiment of the perfusion balloon, an external wrap isplaced around the five previously described balloons. This outer wrapserves to further bond or hold the five balloons into apposition witheach other but also to provide a compartment between the outer wrap andthe five balloons. This outer compartment can be exposed to internalpressure from a fluid and can be used to provide dilatation capabilitiesto the valve leaflets. The outer compartment can be formed into adog-bone shape if desired and the characteristics of the otherembodiments described in this disclosure can be applied to this outerdog-bone-shaped balloon outer wrap or covering. An internal wrap canalso be located in the central region between the five balloons. Thisinternal wrap can serve as a flow conduit path for blood perfusion andcan also be attached to each of the five balloons to provide stabilityto the overall perfusion balloon structure.

Methods for forming the perfusion balloon are also described. One canform the equivalent of five individual balloons by using a forming tooland two balloons having a larger and smaller diameter. The largerdiameter balloon forms approximately the outer half of each of the fiveballoons and the smaller balloon forms the inner half of each of thefive balloons. The manifold of the inflation fluid from one balloonportion to another portion can be accomplished using techniques thatwill not compromise balloon integrity. A temporary valve can be locatedin the central perfusion area to ensure that systemic blood pressure ismaintained during the inflation procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments ofthe invention are capable of will be apparent and elucidated from thefollowing description of embodiments of the present invention, referencebeing made to the accompanying drawings, in which

FIG. 1 illustrates a side view of a balloon catheter according to thepresent invention;

FIG. 2 illustrates the balloon catheter of FIG. 1 in a first state ofinflation according to the present invention;

FIG. 3 illustrates the balloon catheter of FIG. 1 in a second state ofinflation;

FIG. 4 illustrates the balloon catheter of FIG. 1 in a third state ofinflation;

FIG. 5 illustrates an example pressure inflation curve of the ballooncatheter of FIG. 1;

FIG. 6 illustrates an side view of a balloon catheter and diametersensing device according to the present invention;

FIG. 7 illustrates an inflation device according to the presentinvention;

FIGS. 8-15 illustrate various techniques for providing balloon regionswith different compliancy according to the present invention;

FIG. 16 illustrates a side view of a balloon having a plurality ofbraided members according to the present invention;

FIGS. 17 and 18 illustrates a side view of a dual balloon catheteraccording to the present invention;

FIG. 19 illustrates a side view of dual balloon catheter according tothe present invention;

FIG. 20 illustrates a side view of a dual balloon catheter according tothe present invention;

FIG. 21 illustrates a side view of a multi-balloon catheter according tothe present invention;

FIG. 22 illustrates a cross sectional view of the multi-balloon catheterof FIG. 21;

FIG. 23 illustrates a side view of a multi-balloon catheter according tothe present invention;

FIG. 24 illustrates a cross sectional view of the multi-balloon catheterof FIG. 23;

FIG. 25 illustrates a side view of a multi-balloon catheter according tothe present invention;

FIG. 26 illustrates a side view of a multi-balloon catheter according tothe present invention;

FIG. 27 illustrates a cross sectional view of the multi-balloon catheterof FIG. 26;

FIG. 28 illustrates a cross sectional view of a multi-chamber ballooncatheter according to the present invention; and,

FIG. 29 illustrates a cross sectional view of a multi-chamber balloon ofFIG. 28 in a molding chamber.

DETAILED DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIGS. 1-4 illustrate a preferred embodiment of an aortic valvuloplastycatheter 100 with a non-compliant proximal region 102C, a non-compliantdistal region 102A a semi-compliant waist 102B according to the presentinvention. The semi-compliant waist is formed of a resilient elastomericmaterial that can return to its initial shape after multiple inflations.Generally, these regions 102A, 102B and 102C inflate to a dog bone orhourglass shape at certain inflation pressures to help achieve a desiredposition of the balloon 102 within the aortic valve 120. As described ingreater detail below, the semi-compliant waist 102B can further expandagainst the annulus 118 of the valve 120, helping the user determine thesize of the annulus 118 and thus an appropriate replacement valve size.

The valvuloplasty balloon 102 is preferably disposed on a distal end ofa catheter body 104, and delivered over a pigtail-end guidewire 106. Atleast one passage within the catheter body 104 is in communication withthe balloon 102 to allow inflation by liquid (or optionally gas).

It should be understood that the present valvuloplasty catheter 100 canbe created and used according to the techniques set forth in U.S. PatentPublication No. 2005/0090846, the contents of which are incorporated byreference.

In operation, the valvuloplasty catheter 100 of the present invention isintroduced through the femoral or brachial artery using a Seldingertechnique to place a vascular sheath introducer in the peripheralvessel. Alternately, the valvuloplasty balloon catheter of the presentinvention can be placed transapically antegrade across the aortic valvevia a surgical intercostal incision. For the transapical approach thedistal bulb of the dog-bone-shaped balloon would be placed into theaortic sinus rather than the proximal bulb as when using thetransfemoral approach. For the sake of simplicity, all furtherdescription will be made with respect to the transfemoral approach.However, it should be understood that a variety of different placementprocedures are possible according to the present invention.

Returning to the transfemoral approach, a guidewire is placed across theaortic valve and the valvuloplasty balloon catheter 100 is advancedretrograde over the guidewire such that the pigtail 106 is positioned inthe left ventricle. Next, using fluoroscopy or other imaging techniques,the balloon 102 is placed within the valve 120 so that the distalportion 102A is positioned in the left ventricle outflow tract 114, thewaist 102B is positioned at the annulus 118 and the proximal portion ispositioned against the leaflets 116 in the aortic sinus 112.

As seen best in FIG. 2, the balloon 102 is inflated to a pressure ofapproximately 0.1 to 0.5 ATM (i.e., the pressure inside the balloon 102is slightly higher than the pressure outside of it, about 0.2 ATM). Atthis pressure, the waist 102B is prominently undersized relative to theproximal portion 102C and the distal portion 102A as well as the annulus118. This undersized waist 102B helps “center” or position the waist102B at the annulus 118 and therefore achieve desired positions of allportions of the balloon 102. A slippery agent such as silicone oil or ahydrophilic coating can be applied to the exterior surface of theballoon to enhance this centered orientation. Alternately the outsidesurface of a portion of the balloon can be textured or roughened to helphold the balloon in position following inflation.

Next, the pressure in the balloon 102 is further increased; causing thesize of the proximal portion 102C to increase as shown in FIG. 3 andbegin to push the leaflets outwards. This pressure can range between 0.5and 5 ATM and preferably between 1-2 ATM. The size increase of theproximal portion 102C pushes the valve leaflets 116 open, cracking thecalcified portions and further creating hinge points.

The waist region 102B also increases in diameter at the previouslymentioned pressure due to the compliant nature of the material in thisarea. The distal portion 102A may further increase somewhat in size,depending on variation in the anatomical features in the outflow tract.However, the expansion of the distal portion 102A is ultimately limitedby the non-compliant material construction. Since the blood flow canonly be blocked for a short period of time, the balloon 102 is quicklydeflated after a short period of time.

After the leaflets 116 have been “hinged” to an acceptable amount, theuser can use the catheter 100 to estimate the size of the annulus 118when subjected to an internal dilating load and therefore determine theappropriate size of the replacement valve to implant. The followingmethods are described to help determine the fully stretched diameter ofthe annulus 118.

Preferably, to determine the valve stretch diameter, the pressure withinthe balloon 102 is once again increased to expand the balloon 102 beyondthat shown in FIG. 3 to that of FIG. 4. Contrast liquid is injected intothe balloon 102 to allow it to show up on imaging devices (e.g.,fluoroscopy, x-rays, etc.). Since the waist 102B is composed of asemi-compliant material, the further increased pressure causes the waist102B to extend outward. The proximal region 102C and distal region 102Aremain at relatively the same diameter because these regions areconstructed with a non-compliant material. As the pressure increases,the waist 102B extends radially outward until it contacts the annulus118 as seen in FIG. 4.

Once the waist 102B has reached the annulus 118, the valve 120 can beimaged. This image illustrates the contrast liquid in the balloon 102and therefore the shape of the waist 102B, which can be visualized andmeasured. Alternately, radiopaque markers may be embedded or otherwiselocated at the waist 1026 for fluoroscopic imaging purposes.

The user can help determine when the waist 102B has reached the annulus118 by monitoring the change in pressure within the balloon 102 versusthe change in balloon volume, or the change in pressure versus time ifthe volume rate of infusion of fluid into the balloon is maintained at aconstant rate. A pressure manometer 122 or a pressure transducer can beconnected in parallel with an inflation syringe at the proximal end ofthe catheter 100. Alternately a pressure transducer located in or nearthe balloon or in fluid communication with the balloon can also providea pressure measurement. The pressure transducer can be a wirelesstransducer if desired. In this case an RF signal can be sent from thetransducer to a receiver located outside the body of the patient toindicate pressure within the balloon.

FIG. 5 illustrates an example graph that illustrates how pressure maychange in an example balloon 102 over time as fluid volume is injectedinto the balloon at a constant rate or versus balloon volume. As theballoon 102 initially inflates, the proximal region 102C and distalregion 102A inflate and the waist inflates to its equilibrium, lowpressure, state. Since these regions 102A and 102C are composed ofnon-compliant materials, the pressure within the balloon 102 remainsrelatively unchanged as the unconstrained balloon begins to fill withfluid (e.g., pressure slope 130 is relatively flat and at a lowpressure). As the proximal region 102C and distal region 102A reach thelimit of their non-compliant expansion, the pressure within the balloonbegins to increase (e.g., relatively increasing pressure slope 132)causing the waist 102B to expand beyond its equilibrium, low pressure,state. This pressure change during the expansion of the waist 102Bgenerally follows a low upward slope 132 indicative of the compliance ofthe waist material until the waist 102B contacts the annulus 118, whichsignificantly limits further expansion of the waist 102B. Therefore, theannulus 118 causes in an inflection point 133 in the pressure versusrelative or absolute balloon volume curve followed by an increase in theslope 134 that is indicative of the compliance of the annulus and thewaist. The absolute volume of the balloon can be controlled by aconstant volume pump and monitored to track the absolute volume injectedinto the balloon. Alternately, the constant volume pump can be used tocontrol the relative volume of fluid injected into the balloon and therelative volume change can be plotted versus relative change in balloonpressure. If the fluid is injected into the balloon at a constant rate,then the slope 134 for the slope of FIG. 4 can represent the change inpressure versus time after contact is made for the waist with theannulus.

The physician or operator has the capability with the present inventionof providing a controlled valvuloplasty procedure with application of acontrolled force being applied to the annulus. As the balloon waistcomes into contact with annulus, the inflection point or change in slopeof the pressure curve as shown in FIG. 5 is observed. At this point thepressure force within the waist is balanced by the constrictive force ofthe waist and very little force is being applied to the annulus. Thephysician or operator can continue to increase the pressure within theballoon and thereby apply only this incremental pressure above theinflection point pressure to the annulus. Since only this incrementalpressure is being applied to the annulus, the annulus is protectedagainst dissection that can occur if it were exposed to a large force.The slope of the pressure curve above the inflection point is alsoindicative of whether the annulus is a softer annulus or whether it ishard and calcified. Therefore the physician or operator is able toassess the effective modulus of the annulus by observing the slope ofthe pressure curve above the inflection point.

In this respect, when the user determines that the slope of the pressurechanges from a slope similar to slope 132 to slope 134 (i.e., theinflection point 133), the waist 102B has likely contacted the annulus118. At that point, the user can image the valve 120 as previouslydescribed to determine the annulus diameter. Alternately, the user ormanufacture may determine the size of the waist 102B of balloon 102 atdifferent pressures prior to a procedure. Therefore, the user can lookat the pressure reading for the inflection point 133 to estimate thesize of the waist 102B.

Preferably, a computer and computer software (e.g., specialized pressuredisplay device or a PC) can be used to record and display the pressurein the form of a graph. The user can monitor the graph to manuallydetermine the inflection point 133 and therefore the size of theannulus. Alternately, the computer software may monitor pressure data(e.g., the slope) and automatically determine the inflection point 133and convert that pressure value to a diameter size.

FIG. 6 illustrates another preferred embodiment of an aorticvalvuloplasty catheter 142 that is also capable of measuring thediameter of the annulus 118 of the valve. Generally, the valvuloplastycatheter 142 is similar to catheter 100 shown in FIGS. 1-4. A sensor 144can be located at or around the waist 102B of the balloon 102 to measurethe expansion.

For example, the sensor 144 may include a resistive material formed intoa ring around the waist region 102B or a portion of the waist region asshown in FIG. 6. Upon stretching of the waist 102B, the resistance ofthe material changes and can be detected using a circuit that monitorschange in electrical resistance. In another example, the sensor 144 maybe a piezoelectric material located around a portion of the waist suchthat an electrical signal can be generated as the material is forced tostretch to varying degrees.

Either of these previously mentioned sensors 144 are preferablyconnected to an electrical wire 146 located along the shaft 104 of theballoon to deliver the signal from the balloon 102 to the proximal endof the balloon catheter 140 and to an inflation device that is attachedto the balloon catheter.

In another example, the sensor 144 may include either capacitive coupledor inductively coupled sensors that detect the proximity of one sensorto another and are able to identify changes in the separation betweentwo such sensors. More specifically, components of the sensor may belocated both at the balloon waist 102B and within the diameter of thewaist 102B, on the shaft 104. Hence, as the waist 102B expands, thecomponents of the sensors move apart from each other and can thereforebe measured.

In yet another example, ultrasound sensor 142 can be used to measure thediameter of the waist 102B as it contacts the annulus (e.g., asevidenced by the inflection point 133 in the slope of the pressureversus volume curve). Small ultrasound sensors 142 are located in theinterior of the balloon along the catheter shaft 104. Such ultrasoundsensors are used in interventional balloon catheters and in otherdiagnostic devices to measure vessel diameter or the diameter ofsurrounding structures. The diameter measured by these sensors 142during the inflection point 133 is then indicative of the diameter ofthe annulus 118. The ultrasound sensor 142 may also be capable ofidentifying the perimeter of the annulus and this information can beconverted to an annulus diameter.

In a preferred embodiment, the distal portion 102A achieves maximumpredetermined diameter at approximately 0.3-1 ATM. The proximal portion102C achieves its maximum predetermined diameter after the pressure hascaused the leaflets to become displaced outwards at approximately 0.5-2ATM. Preferably, the catheter 100 (or catheter 140) is configured to notexceed approximately 3-5 ATM of pressure so as to remain safelycontained by known dilatation balloon materials.

A desired pressure limit (e.g., 3-5 ATM) within the balloon 102 can beachieved with the inflation device 150 shown in FIG. 7 (describedelsewhere in this specification). For example, a cutoff safety orpressure spill-off valve contained in a balloon inflation device can beactivated at a desired maximum pressure.

In one balloon embodiment, the waist 102B assumes an oval shape wheninflated to better engage the generally non-circular valve cross sectionof the annulus 118. The waist 102B can cause the annulus to become roundas it comes into contact with it or applies an outward force against theannulus as the annulus becomes rounded. The force applied by the waistoutward onto the annulus is, however, less than the internal pressure ofthe balloon since the semi-compliant waist 102B is providing an inwardconstrictive force that acts to balance the outward acting internalpressure. The entire internal balloon pressure also acts to cause theleaflets to be pushed outward into the sinus region.

Preferably, the proximal region 102C has an inflation diameter that issized similarly but slightly smaller than the aortic sinus 112 that islocated adjacent to the ascending aorta 110. This diameter size of theproximal bulbous region 102C provides greater distension to the leaflets116 and thereby more effectively crack the calcium deposits than couldbe attained with a standard cylindrically shaped balloon.

Alternately, the balloon 102 can be constructed such that when aspecified volume of fluid is place within its interior, the waistdiameter is directly known. Thus by controlling and knowing the volumeof inflation fluid that is delivered into the balloon along withmonitoring the pressure within the balloon, the waist diameter can bedetermined (by knowing the volume) when the waist comes into contactwith the annulus (by monitoring the pressure and noting the inflectionpoint). A positive displacement fluid delivery device such as a syringecan be used to assess the volume of fluid delivered to the balloon. Apressure graph similar to FIG. 5 can be created for monitoring purposesin which the y-axis again represents the balloon pressure but the x-axisrepresents the absolute volume delivered to the balloon rather than arelative volume delivered when the inflation fluid is delivered at aconstant rate.

FIG. 7 illustrates an inflation tool 150 according to the presentinvention used to deliver contrast fluid to the valvuloplasty balloon100. Compression of a handle 152 drives a plunger 160 down a barrel 152to force the contrast fluid into the valvuloplasty catheter 171. As thelowered plunger 160 near the stops 166, contrast fluid is driven in atwo stage process.

In the first stage, contrast fluid travels at a rapid rate out of theoutflow port 182 to fill the balloon 100 with approximately 90% of itsballoon volume in approximately 1-5 seconds. In the second stage, thetop plunger then drives the remaining about 1-2 cc of fluid through theside holes 178 located in the lower plunger at a controlled rate that islimited by fluid resistance through the holes 178.

To remove the fluid from the balloon 100, a toggle switch 158 isactivated to allow a compression of the handle 152 to force the plungerupward instead of downward, creating a vacuum that causes the contrastfluid to be removed rapidly through the one way valve 168 located in thelower plunger 180. The lower plunger 180 rides upward from the vacuumforce until it comes into contact with the stops 166 and is ready forthe next deliver of fluid to the balloon.

A variable resistor 156 serves as a fluid volume measure to track therelative amount of fluid delivery (or change in volume delivered) to theballoon 100. Other digital position sensors can also be used to detectthe relative movement of the plunger with respect to the barrel of thedelivery device. The sensor that detects fluid volume change in thebarrel sends an electrical signal to the display 164 located on theinflation device, the balloon catheter, or on a separate member locatedoutside of the patients body.

A balloon pressure transducer 184 is located in the balloon 100 near thejunction with the catheter shaft 104. A barrel pressure transducer 172is also located in the delivery device or in the barrel 162 of theinflation tool in order to account for balloon pressure variability dueto inertia and shaft compliance. Only one of the pressure transducersmay be needed to ensure that the pressure reading is an accurate measureof the balloon pressure. The pressure reading representative of theballoon pressure and the relative balloon volume are detected by areadout display 164. The readout display comprises a computer chip alongwith the electronic circuitry to receive the pressure and relativeballoon volume signals, store them, and plot pressure versus relative orabsolute balloon volume. The computer chip also computes the slope ofthe pressure versus volume curve and is able to detect a change in thisslope.

When the slope of the pressure versus volume curve reaches an inflectionpoint or a change in slope, this detected pressure will be captured bythe computer chip and displayed along with the diameter of the balloonat this pressure. The diameter of the balloon will be calculated by thecomputer chip and is reflective of the modulus of the waist region andthe pressure at the inflection point. This waist diameter will thenindicate the annulus diameter which will be displayed by the readoutdisplay.

It is further noted that the inflation device can also be operated suchthat fluid is delivered to the balloon catheter at approximately aconstant rate. In this case the computer chip found in the readoutdisplay would be receiving pressure data and storing it versus timeelapsed since the start of fluid injection into the balloon. Thecomputer chip would in this instance plot pressure versus time and wouldcompute the slope of this curve and detect a change in this slope. Whenthe slope of the pressure versus time curve reaches an inflection point,the pressure at this point is captured by the computer chip and isconverted to a waist diameter reading that is displayed by the readoutdisplay.

Preferably, the balloon 102 comprises a single internal compartment.However, multiple compartments with their own inflation lumens are alsopossible. For example, the balloon 102 may include a proximalcompartment, a middle waist compartment and a distal compartment, eachallowing for individual inflation control.

The balloon 102 can be made from a variety of different materials knownin the art for use in balloon catheters. For example, compliant orsemi-compliant material can be selected from nylon, Surlyn, vinyl, PVC,polyethylene, polyurethane, Pebax, olefins or copolymers of thesematerials. In another example, non-compliant material can be selectedfrom PET (Dacron), Teflon, polyimide, Kevlar wraps, metal, polymer orfibrous material. In a further example, compliant or semi-compliantmaterial can be made to be relatively non-compliant by applyingcrosslinking such as ebeam, chemical or other crosslinking treatments.In yet another example, a non-compliant material can be made morecompliant or semi-compliant by treating it with ebeam, chemicaltreatment or other process to weaken the molecular structure of theballoon material.

In one embodiment, the outside of the balloon 102 can be coated with adesired drug for elution during a procedure. For example, olimus orpaclitaxel type drugs could be used or other types of drugs to offsetthe local deposit of calcium and possibly alter osteoblast calciumdeposition.

As previously described, the balloon embodiments of the presentinvention may have regions of different compliance (e.g., non-compliant,semi-compliant and compliant). Some example techniques for creatingballoons with these characteristics are described in greater detailbelow.

In one example shown in FIG. 8, a balloon 200 can be created byextruding a first tube 206 of semi-compliant material and a second tubeof non-compliant material 204. One or more segments of the non-complianttubing 204 can be placed over the semi-compliant tubing 206concentrically in the region or regions that are to be non-compliant(e.g., proximal section 102C and distal section 102A). This tubingassembly is then placed into a heated mold 202 that forms the externalshape of the balloon 200 while pressure, internal to the tube assembly,is also applied to maintain desired contact with the mold contours. Anadhesive agent or thin polymer layer can also be applied between theconcentric tubes 204 and 206 (preferably prior to the mold process) toenhance bonding to each other.

Additionally, axially oriented fibers can be adhered or embedded acrossthe waist region to help reduce axial length increase in the waist asthe balloon 200 is exposed to increasing pressures. The axial strandscan be individual polymeric or metallic strands or multifilament strandsthat are bonded to the outside of the waist region. Alternately, thestrands can be sandwiched between two layers of balloon material.

In another example seen in FIG. 9, a balloon 208 can be created bycoextruding two tubes having an inner tube 206 with semi-compliantmaterial and an outer tube 204 having non-compliant material. A portionof the outer, non-compliant tube 204 can be etched away in a regiondesired to be semi-compliant (e.g., the waist 102B). Preferably, laseretching, plasma etching, mechanical etching or chemical etching areused. The non-compliant tube 204 can be partially etched through orfully etched through, leaving the semi-compliant tube exposed 206. Next,the coextruded tubes are placed in a heated mold where pressure internalto the tube presses the tube against the mold contours to form thedesired mold shape. Alternately, the coextruded tubes can be moldedprior to etching of the non-compliant material 204. After molding, theouter tube can be further etched in locations to more precisely achievea desired compliance (or non-compliance).

In another example construction method, a non-compliant outer layer canbe applied over the outside of the entire semi-compliant balloon andaxial slits located in the waist region can be formed in the outernon-compliant layer in the waist to allow the semi-compliant waist toenlarge in diameter when exposed to increasing internal pressure.

In yet another seen in FIG. 10, a balloon 212 can be created by moldinga semi-compliant material 206 into a desired balloon shape. The areasdesired to be semi-compliant can be masked or covered with a mask 214and a thin non-compliant polymer layer 216 can be applied onto theunmasked regions (e.g., the distal region 102A and proximal region 102Cof balloon 102). Such noncompliant materials can include polyimide,polyethylene terephthalate, fiber reinforced polymers, and many polymerscommonly used for noncompliant balloons. Preferably, the non-compliantpolymer 216 can be applied by spray or dip coating and can be furthertreated to provide crosslinking to enhance the non-compliant properties.Regions of the balloon can be masked during various stages of theprocess to provide various levels or areas of compliance andnoncompliance.

In yet another example seen in FIG. 11, a balloon 218 can be created bymolding a non-compliant material 204 into a desired balloon shape. Next,the non-compliant material 204 can be post processed in desired areas(e.g., the area that would become the waist 102B of balloon 102 in FIGS.1-4) to achieve semi-compliant characteristics. This post processing mayinclude ebeam, chemical treatment or mechanical treatment. In a morespecific example, ebeam will reduce crosslinking in most fluoropolymermaterials and therefore may increase the compliance in the treated area.

In another example shown FIG. 12, the balloon 222 can be created bymolding a semi-compliant material 206 into a desired balloon shape.Next, the semi-compliant material 206 can be post processed in desiredareas to achieve non-compliant characteristics. This post processing caninclude, for example, ebeam to cause crosslinking between mosthydrocarbon backbones such as those found in polyethylene. Again, a mask214 can be used to prevent treatment of areas desired to besemi-compliant.

In yet another example seen in FIG. 13, a balloon 226 can be created bymolding non-compliant material 204 in a desired balloon shape andplacing elastic members 228 around the region that is desired to besemi-compliant shown in FIG. 6. The elastic wrap preferably has a nativediameter (i.e., a mostly or partially unstretched diameter) that issmaller than the native diameter of the non-compliant balloon shape. Thenon-compliant material 204 adjacent and near the elastic wrap 204 may beforced to fold, bend or wrinkle to allow for semi-compliant expansionduring use.

In yet another example, a balloon can be created by molding a materialwith a plurality of circumferential fibers embedded or otherwise locatedalong the axial length of the balloon. By increasing or decreasing thespacing of these fibers, the compliance can be increased or decreasedrespectively. Additionally, the fibers can be increase or decreased indiameter to further modify the compliance characteristics of theballoon.

In another example seen in FIG. 14, a balloon 230 can be created by asemi-compliant material 206 that is molded to a balloon shape. Anon-compliant material 204 is separately molded to the balloon shape.The distal and proximal portions are cut off of the non-compliantmaterial 204 and placed over the distal and proximal ends respectivelyof the semi-compliant balloon material 206. Pressure and temperature isapplied to the balloon 230 in a mold to fuse the layers together oradhesive or polymer can also be applied between the layers to enhancebonding.

In another example seen in FIG. 15, a balloon 232 can be created by amolding a semi-compliant material 206 and separately molding anon-compliant material 204 into a balloon shape. The middle waistportion of the non-compliant material 204 is weakened to create a morecompliant region 234. The non-compliant material 204 is placed over thesemi-compliant material 206 and the balloon 232 is placed back in themold with pressure and heat to fuse the materials 204 and 206 togetheras previously described. Adhesive or similar bonding material may alsoor alternately be used between the materials 204 and 206.

In another embodiment shown in FIG. 16, a balloon 326 is formed withbraided members 238 that extends at least through the semi-compliantwaist region 236B. The braid can be constructed from multifilamentstrands of polyethylene terephthalate, polyethylene, or other polymer orthin metal stands. The braid can be bonded to the balloon using UVcurable acrylic, polyurethane, or other bonding agent. The braid willallow the waist 236B to enlarge in diameter while causing the waist 236Bto reduce in length. This balance will allow the inflection point 133 inthe delta pressure/delta volume curve to become more pronounced ascontact is made by the waist 236B with the annulus 118. The braidedmembers 238 can also ensure that the waist 236B does not over extend indiameter and cause dissection to the annulus 118. The braided members238 can also help to hold the non-compliant regions 236A and 236B suchthat they do not expand in diameter and thereby help to improve theobservation of the inflection point 133. The braid angle of the braidedmembers 238 in the waist region 236B may, for example, be more axiallyoriented than that in the bulbous end regions 236A and 236C of theballoon 236.

Optionally, a third fiber having substantially a circumferentialdirection and having a diameter approximately equal to an upper limitdiameter can be braided into a standard braid that has a fiber anglewith respect to the axis of about 42-75 degrees. The presence of thethird fiber may limit diameter of the braid such that it cannot extendbeyond the upper diameter limit set by the circumferential strand.

In another embodiment, braided member can be bonded over the balloon inits configuration that is not yet expanded. Preferably, this bondingoccurs when the waist is expanded to approximately an 18 mm diameter.Here the braid is forced into a smaller diameter by pulling apart oneach end of the braid. This smaller diameter portion is then bonded tothe waist. Further, the braid is bonded to the larger diameternon-compliant end portions of the balloon.

An alternate method for forming one embodiment of the balloon includesforming a zig-zag shape from a multifilament strand of PET, Dacron,nylon, or other high strength material ranging in diameter from0.0005-0.003 inch and preferably 0.001-0.002 inch. Each micro fiber ofthe multifilament strand can be approx. 5-20 microns in diameter. Alsonitinol multifilament or monofilament strands of similar dimensions canbe used. The zig-zag shape can have an angle from the average axisdirection of 30-60 degrees and preferably 40-50 degrees for a diameterchange for the waist of 18 to 24 mm as the zig-zag strand becomesstraightened under force. The zig-zag strands are formed by placing thegenerally straight strand along a comb-like fixture that forces thestrand between the opening of another the combs-like fixture. Similarlythe teeth of a cross cut wood saw can be used as a mold to force thestrands into the valleys of another cross cut saw. The strand is thenheat treated to form a zig-zag pattern while being held by the fixtureor mold.

With the balloon in a smaller diameter configuration, the zig-zag strandis wound around the waist region (preferably inflated to about 18 mm indiameter) in a spiral manner. Note that circles of zig-zag material canalso be used. For example a zig-zag can be cut from a tube or nitinolusing a laser and placed around the waist of the balloon. The zig-zagstrands are then bonded to the waist using an elastomeric adhesive suchas silicone, polyurethane, a copolymer of these polymers, and otherpolymers.

In another embodiment, a dog-bone shaped balloon can be formed by anapproximately 25 mm in diameter cylindrical balloon composed of anon-compliant material such as PET or nylon. In the central region ofthis balloon where the waist is intended to be located, thenon-compliant material is folded. This can be done by the initial moldthat forms the balloon to begin with such that it has a rippled orcorrugated shape running axially in the waist region. Alternately, itcan be formed as a post process by placing a metal element inside theballoon from each end opening and a mold outside the balloon andallowing the balloon material to be forced into a rippled or corrugatedshape. The corrugated shape will allow the non-compliant balloon to foldin a controlled manner when it is expected to constrict down due to theelastomeric waist material (previously described).

As a second step, an elastomeric waist can be formed that extends from asmall diameter of about 18 mm in the center of the waist to a diameterof approx 24 mm at the ends of the waist. This component can be formedfrom a molding operation or an extrusion operation followed by a postprocessing method to form or mold the proper shape. The material can besilicone, polyurethane, a copolymer, or other elastomeric polymer.

The non-compliant balloon is then expanded out to its expandedconfiguration at a lower pressure ranging from 0.1-4 Atm. The waist isthen placed over the center of the non-compliant balloon and bonded tothe center. Upon release of pressure, the waist portion of the ballooncontracts due to the shape and force of the waist portion. Uponexpansion to a larger pressure, the non-compliant balloon materiallocated in the waist region ensures that the waist cannot expand beyond25 mm.

As previously described, the waist 102B of the balloon 102 (FIGS. 1-4)is preferably compliant or semi-compliant, meaning its diameter willdiffer between the proximal portion 102C and distal portion 102A,depending on the inflation pressure within the balloon 102. In otherwords, the non-compliant regions will remain relatively constant indiameter during inflation while the semi-compliant regions will growwith more pressure For example, the waist 102B may be 16-20 mm indiameter in its equilibrium state and capable of stretching to engagethe annulus at 19-25 mm in diameter whereas the proximal and distal endsremain at a relatively fixed diameter ranging for approximately 23-28mm.

Preferably, the waist 102B of the balloon 102 is “undersized” in itsequilibrium, low pressure, state (i.e., sized smaller relative to theannulus) by about 3-5 mm. For example, if the target annulus 118 of thepatient's valve 120 is about 23 mm, a balloon 102 with a waist 102B atequilibrium is about 20 mm. Preferably, this example waist 102B grows by2 mm at a pressure of 2 ATM to a diameter of 22 mm. At this diameter of22 mm and an internal pressure of 2 ATM, the outward force exerted uponthe annulus is about zero since it takes 2 ATM of pressure just to reach22 mm in diameter. As this example balloon 102 becomes furtherpressurized to 3 ATM, its waist 102B grows further to 23 mm and it maycome into contact with the wall of the annulus 118, but would likely notexert much, if any pressure on the annulus 118 (since the waist 102Bwould just begin to engage in contact).

In contrast, the proximal portion 102C and distal portion 102A apply anoutward force of about 3 ATM against the leaflets 116 and left ventricleoutflow tract 114 since these portions 102A and 102C are non-compliantand are in contact with these structures starting at the equilibriumpressure. If the pressure was further increased to 4 ATM, only 1 ATM ofoutward force maximum would be applied to the annulus 118. In thisexample, it is believed that exposure of the annulus 118 to a pressureof 2 ATM, for example, or less will not result in a dissection (i.e.,damage). If the actual annulus diameter was 22 mm and the waist came into contact with the annulus at 2 atm, the annulus could be exposed to 2ATM of pressure if the internal balloon pressure was 4 ATM.

Further, the waist 102B preferably self-locates such that the waist 118automatically locates over the annulus 118, thereby avoiding damage toother portions of the valve 120. For example, if the waist 102B of theballoon was located low into the left ventricle outflow tract 114, thenthe proximal portion 102C, normally located in the sinus 112, may expandin the annulus 114 and possibly cause dissection. If the waist 102B wassomehow positioned in the sinus 112, then the inflated waist 102 wouldnot achieve a diameter capable of “cracking” the calcified leaflets 116at their base. The length of the waist 102B must be adequately sized tothe annulus 118 to avoid similar outcomes.

To aide in the self positioning, the outside of the balloon 102 can beslippery so as to enhance its ability to “slide” into a desired positionwith the waist 102 positioned over the annulus 118. Alternately, theouter surface of the balloon can be textured or roughened to help holdthe balloon into position during the inflation.

Note that the term non-compliant, which has been used in thisspecification, refers to material that is relatively inelastic. In otherwords, such material has little or no stretch under most, intendedcircumstances, such as application of moderate pressure. The termscompliant or semi-compliant, which have been used in this specification,refer to material that includes at least some elasticity. In otherwords, such material will stretch with little or no damage to thematerial under most, intended circumstances, such as application ofmoderate pressure. The waist material should preferably also beresilient such that it returns to its initial diameter when the pressureis reduced.

The specific balloon description presented below is an example of oneballoon size that is intended to cover a size range of annulus diametersfrom 21 to 24 mm. It is a dog-bone shaped balloon with a waist that issemi-compliant and non-compliant bulbous end-regions. For the purposesof this specific example, FIG. 1 will be further referred to.

The balloon 102 has a length 111 of between about 40-80 mm andpreferably 50-70 mm. Regions 102A and 102C are non-compliant whileregion 102B is semi-compliant. The balloon 102 has a working pressure ofbetween about 4-5 atm; a burst pressure between about 6-7 atm with thetear direction preferably in the axial direction. The wrap profile ofthe balloon 102 is about 10-12 Fr and the catheter shaft 104 ispreferably between about 9-12 Fr. The guidewire lumen is configured forover the wire techniques with about a 0.036″ wire. The balloon waist102B has a length 109 when of about 5-10 mm axial length at 0.1 ATM andabout an 18-21 mm maximum diameter 105 in its center. Preferably, eachsection 102C and 102A have a maximum diameter 103 and 107 of betweenabout 25-56 mm.

The following are example measurements of the balloon waist 102B atvarious pressures:

Balloon Pressure Diameter 0-0.1 ATM 18 1 ATM 19.5 2 ATM 21 3 ATM 22.5 4ATM 24

Preferably, two circumferential Angiographic marker bands are located onthe surface of the balloon 102 and optionally on the central shaft 104,within the balloon and near the waist area 102B. Such marker bands canbe a ring of radioopaque material swaged or bonded onto the cathetershaft or applied via vapor deposition or coating process onto theoutside of the balloon

Balloon ends can be formed at 4 mm OD at each end. One example placesapproximately a 0.038 in ID×0.046 in OD tubing through the cathetershaft and through the balloon to provide passage for a 0.035 inchguidewire. The distal end of the balloon is bonded to the guidewiretubing. Some expansion in the length of the balloon may occur underpressure due to expansion of the waist. It may be desirable to reduceany balloon curving that occurs as the balloon is expanded underpressure by preferably using a guidewire tubing with similar axialexpansion as the balloon.

In the previous example, the waist is suggested to undergo an expansionfrom about 18 mm to 24 mm as the pressure increases from a smallpressure above zero ATM (i.e., 0.1 ATM) to 4 ATM. This waist complianceis described as a linear compliance. However, since most elastomericpolymers are not linear, it is desirable that the middle of the waistachieves the diameters indicated in the example at the two points whichoccur at 2 ATM and 4 ATM. These two middle waist diameters are 21 mm and24 mm at 2 ATM and 4 ATM, respectively. Preferably, the diameter of themiddle of the waist is smaller than 18 mm in its natural state (i.e., atapprox zero pressure) in order achieve the 21 mm and 24 mm data points.

In some examples, the semi-compliant waist is joined to non-compliantbulbous ends. This junction of a semi-compliant material with anon-compliant material can generate a discontinuity that may result inbreakage. A small transition region may reduce this breakage although itshould be noted that such a transition may not be appropriate for allballoon materials and designs. If a transition region is necessary, thenthe transition region can be formed in the waist, thereby making theaxial length of the waist somewhat smaller than the 5 mm-10 axial lengthlisted on the drawing.

The non-compliant bulbous regions 102C and 102A are intended to maintaina fixed diameter from 1 ATM to 4 ATM. If the non-compliant regionsstretch with an increase in pressure, it may be difficult to detect thestretching waist by monitoring the balloon pressure. Therefore thebulbous regions should preferably be made of a material that resists anycircumferential stretching.

As discussed in U.S. Publication No. 2005/0090846, the contents of whichhave been previously incorporated by reference in this application, analternate embodiment of a balloon is possible according to the presentinvention, including a non-compliant waist and semi-compliant proximaland distal portions. In one example, the balloon can have thecharacteristics described below, although it is recognized that thisballoon embodiment may not have the ability to measure the annulus in amanner described for the semi-compliant waist balloon of FIGS. 1-4.

The balloon includes a waist that is non-compliant and at least one endportion that is semi-compliant. However, both end regions may also besemi-compliant. The end portions are able to expand under pressurethereby allowing the bulbous proximal portion to push the leaflets backto an amount that is dependent upon the internal balloon pressure, whilethe waist cannot over-distend the annulus.

An internal pressure of approx 2 atm can cause the proximal portion ofthe balloon to expand outwards by approximately 10-20% beyond itsequilibrium size causing the diameter of the balloon to extend fromapprox 20 mm to 24 mm. The balloon can be constructed such that theballoon shape is bulbous in a manner described earlier where the waistis smaller than the bulbous regions by approximately 15-25%.Alternately, the balloon can be almost cylindrical in shape with thewaist only approximately 10% smaller than the bulbous ends at a pressureof 1.5 atm. The waist can range in length from 1-10 mm.

The balloon can be constructed by applying a non-compliant material, aspiral wrap, a braid, or woven fabric in the waist region of asemi-compliant balloon to make the waist into a non-compliant region.Balloon strengthening can alternately be applied to the waist viachemical or other means of crosslinking.

In another alternate embodiment, the entire balloon may be composed ofnon-compliant material. A dog-bone shaped balloon with a non-compliantwaist approach may require a close estimate of the annular diameterwithin 1 mm and therefore the balloon waist should be sized to matchthis diameter. In one example, a dog-bone shaped balloon is created suchthat it is entirely non-compliant and provides the balloon sizes inincrements of 1 mm annular diameter size variations.

This all non-compliant balloon operates at a pressure ranging from 3 atmto very high pressures of over 10 atm. Safety is obtained by ensuringthat the waist does not grow. Preferably, the dog-bone shaped balloon isslippery so that it moves to self-center the waist at the annulus 118.Failure to self center may result in the larger portions of the balloonbeing positioned at the annulus and thereby causing the annulus todissect.

In another embodiment, a dog-bone shaped balloon is entirelysemi-compliant. Hence, this balloon configuration does not constrict thegrowth of the bulbous end regions of the balloon. The change in thepressure/volume curve that is observed when the waist comes into contactwith the annulus is not as obvious as with other described embodimentssince the end bulbous regions are still able to grow in volume as thepressure inside the balloon is increased.

One difference from the previously described, all non-compliant balloonis that a compliance curve may be used to size the diameter of theannulus. Following contact of the waist with the annulus, the annuluscould increase in diameter due to an increased operating pressure butthe waist would be sized accordingly such that annular expansion wouldnot be significant. The sinus and distal portion of the balloon wouldcontinue to increase proportionally with increasing pressure. Thediameter that is selected for the balloon waist would be set by adiameter that would not stress the annulus. If the material for thissemi-compliant balloon were such that generally higher pressures werebeing used during the inflation and prior to contact of the waist withthe annulus (i.e., greater than 2-5 atm), then the entire balloon couldbe made of the same semi-compliant structure. The internal pressurewithin the balloon would impart very little force to the annulus. Thesafety is gained by ensuring that the annular diameter is larger thanthe waist during leaflet expansion and inflation is terminated soonafter contact of the waist with the annulus. Some operating challengeswith the totally semi-compliant balloon can occur due to continuedexpansion of the bulbous portions of the balloon after that waist makescontact with the annulus, thereby reducing the magnitude of the slopechange in the pressure versus volume curve after the inflection point.

In a manner similar to the previously described, all non-compliantballoon, the balloon may be slippery to ensure that it self centered onthe annulus. If it did not self center, one could easily cause anannular dissection due to placement of the proximal or distal portionsof the balloon in the annulus region. This higher pressuresemi-compliant balloon may be manufactured out of nylon or othersemi-compliant material or it may use a composite wall structure havinga braid or other fiber matrix bonded to or contained within the balloonwall, if the profile was not a limiting factor.

FIGS. 17 and 18 illustrate another embodiment of a valvuloplasty balloon242 according to the present invention. This balloon 242 includes alarger diameter region 242B for expanding against valve leaflets and asmaller diameter region 242A for anchoring in the left ventricle outflowtract. The size of the patient's annulus can be measured by a smallerinner balloon 248 that is located over an inflation port 248 on thecatheter shaft 244 and located within the balloon 242.

The inner balloon 248 has an inner balloon inflation lumen that connectsto port 246, allowing the inner balloon 248 to be inflated first andserve as a positioning balloon that locates this balloon upstream andadjacent to the aortic annulus. The inner balloon can be bonded to theshaft to obtain a shape or profile that best allows positioning of theballoon. Once this balloon is in place, the larger outer balloon can beinflated using a separate outer balloon inflation lumen to dilate theleaflets via the sinus portion of the outer balloon 242.

This sinus portion 242B of the outer balloon has a larger diameter thanthe locator balloon 248 and is sized to push the aortic leaflets outwardinto the aortic sinus. The outer balloon can have a distal shape that iscylindrical as seen in FIGS. 17 and 18, a balloon 250 with proximal end250B and a distal end 250A that follows the inner balloon 248, or aballoon 252 having a bulbous proximal end 252B and a bulbous distal LVOTportion 252A that forms a waist region 252C as seen in FIG. 20.

The outer balloon of the embodiments of FIGS. 17-20 can be constructedusing any of the construction means described in the previousembodiments including non-compliant, semi-compliant or a combination ofboth materials. The outer balloon can, for example, have asemi-compliant waist and be used to measure the annular diameter asdescribed earlier.

The inner balloon can be constructed of either semi-compliant ornon-compliant materials. The inner balloon can also be used to assessthe diameter of the annulus by monitoring its volume and calculating thediameter of the annulus as previously described in this specification.Pressure measurements made in either the inner balloon or between theinner and outer balloon can also be used as described earlier to monitorchange in pressure versus change in volume to identify that contact hasbeen made with the annulus. Various sensors such as ultrasound,piezoelectric, electrical resistance and others can be used along withthis embodiment as described in previous embodiments to measure theannulus diameter.

It should be understood that drugs may be applied the outside of any ofthe previously described embodiments for treatment purposes. Forexample, drugs similar to the “olimus” or “paclitaxel” groups may beused to offset the local deposit of calcium and possibly alterosteoblast calcium deposition.

It is also possible to configure the shape of the balloon 102 to allowperfusion during the procedure. For example, perfusion channels orpassages may be included in the balloon 102.

FIGS. 21 and 22 illustrate a perfusion balloon device 260 that includes5 individual balloons 262A-E or 5 balloon compartments arranged in apentagon shape around a flow area 266. Each of the balloons 262A-E areattached to each other at attachment sites 264. Each balloon 262provides support to the central flow area 266 by intimate contact withtwo other balloons 262. The central flow area 266 for the 5 balloons 262is preferably about 0.48 cm sq, which is though to be enough to maintainadequate perfusion to the brain while the balloons 262 are inflated.Fewer balloons can also be used however this results in a smallercentral flow area. If 3 balloons are used, the area is preferably about0.056 cm sq and for four balloons it is preferably about 0.237 cm sq.The shape is more stable with fewer balloons however the flow area ismuch less. If more than 5 balloons 262 are used, the flow area may beincreased, however the stability of the shape may be reduced.

Each balloon 262 is attached to a central manifold 268 at the proximalend of the balloons 262 such that all of the balloons 262 are inflatedsimultaneously. The flow of blood is provided via access between theballoons 262 at the distal end and flows down the central flow area 266and passes between the balloons 262 at the proximal end. It is notedthat the 5 balloons 262 can be formed such that the balloon inlets arelocated off to one side of the assembly rather than located on thecentral axis of the assembly as shown. Locating the inflation inlet andmanifold off of the central axis would potentially allow for a moredirect flow path for the blood into and out of the assembly.

FIGS. 23 and 24 illustrate a balloon valvuloplasty device 270 which issimilar to the previously described device 260 except for the additionof an external wrap 272 around the outside of the 5 balloons 262. Theexternal wrap 277 is a thin but strong plastic material that also servesas a balloon around the outside of the five balloons 272. The externalwrap 272 can also be preferably attached to the 5 balloons 262 atattachment sites 276. Flow of fluid such as blood can occur through thecentral region 273 located between the five balloons 262.

The attachment of the balloons 262 to the external wrap 272 not onlyprovides stability to the shape of this balloon assembly 270 but alsoallows inflation to occur between each of the balloons on the outside ofthe balloons in external spaces labeled 274 via a separate inlet lumen275 to the external space. Expansion of the external space 274 at anexternal wrap pressure allows the entire structure to provide expansionto external tissue forming a round or continuous shape. It is believedthat the external wrap pressure should be somewhat lower than theballoon inflation pressure such that the balloons are providing an evensupport to this external wrap. The pressure in the external wrappreferably ranges between 1 and 6 ATM and preferably between 2 and 5ATM. The pressure in the 5 balloons may range from 2 to 20 ATM.

A seal must be made between the external wrap and each of the individualballoons 262 separating it from the flow area 266 for the perfused bloodthrough the central flow area 266 of the balloon assembly 270. This flowpassage must be provided at the proximal and distal end of the balloonassembly 270 and includes an attachment with each of the 5 balloons 262.A continuous passage for blood is formed from the central flow area 266through a space located between at least two balloons that arethemselves sealed independently to the outer wrap in the proximal anddistal ends of the balloon assembly.

FIG. 25 illustrates a balloon 280 similar to previously describedballoon 270 formed from the 5 individual balloons 262 but further havingan external wrap 272 that has a dumbbell or lobular shape. A proximalbulbous region 272C provides expansion to the sinus region and thedistal bulb 272A provides positioning support to the balloon assemblysuch that it does not move axially and instead tends to self-center withthe balloon waist 272B located at the annulus of the aortic root. Thefunctionality of the balloon assembly 280 is similar to that describedin FIGS. 1-4. To enhance the overall shape, the waist region 272B can beattached to each of the balloons at attachment points 282.

FIGS. 26 and 27 illustrates a valvuloplasty balloon device 290 that issimilar to the previously described device 270, but with an additionalwrap or tube that forms a passage 292 within the balloon assembly 290.The internal passage 292 provides a confined flow space for the bloodthrough the central portion of the balloon assembly 290. The internalpassage 292 allow for passage of blood from the central flow areathrough the external wrap 272 and allows the external wrap 272 to form acontinuous space separate from the flow area for the blood. The internalpassage 292 forms a seal 294 with the external wrap at the proximal anddistal ends of the balloon assembly.

The perfusion balloons described in FIGS. 21-27 can be formed from 5separate balloons positioned adjacent to each other and having anexternal wrap placed around it. The manifolding of the inflation fluidcan be accomplished in a variety of ways one of which was shown in FIG.21. It is also possible to form the balloon assembly and accomplish themanifolding of fluid in other ways.

Five balloons can be positioned adjacent to each other as describedearlier with openings directly between balloons to allow inflation fluidto access from one balloon to another. Such openings can connect theballoons, thus allowing manifolding of the inflation fluid to each ofthe five balloons. The ends of the balloons can be flattened or foldedand sealed.

The balloon assembly having multiple balloon-type cylindrical shapeslocated adjacent to each other can be formed from two cylindrical tubesthat form the inner half and outer half of the multiple cylindricalshapes. One can form the balloon assembly 300 having five internalcylindrical balloons and an outer wrap from three cylindrical balloonsas shown in FIG. 28. The outer balloon half 302 is a thin walledcylindrical tube; its perimeter is equal to the additive perimeters ofthe outer halves of each of the five balloon-type cylindrical shapesadjacent to each other. The inner balloon half 304 is somewhat smallerthan the outer balloon half and is used to form the inner halves of eachof the five balloon cylindrical shapes.

FIG. 28 further shows how the inner 304 and outer balloon halves 302 arepositioned to effectively form five adjacent balloon-type cylindricalshapes. An inner forming tool 308 and an outer forming tool 306 areplaced as shown in FIG. 29. Heat or other bonding method is used toattach the inner and outer balloon halves 302 and 304 together at theinner/outer attachment points or surfaces. In the region of ballooncontact where an opening 310 is needed to provide passage for inflationfluid, a surface contact seal can be formed such that a leak freeopening can be made within this seal from one compartment to an adjacentcompartment.

An external wrap can be sealed around the outer balloon half asdescribed earlier.

The external wrap can have a cylindrical shape or a bilobular ordumbbell shape as appropriate to its various applications includingvalvuoloplasty. The material can be noncompliant, semicompliant, or acombination of noncompliant and semi-compliant. In one embodiment thewaist region is formed from a semicompliant material and each of thebulbous regions can be noncompliant. Alternately, the entire outer wrapcan be formed from either a noncompliant or a semicompliant material.

The perfusion balloons described above allow dilatation of the aorticvalve leaflets for a longer period of time while allowing blood to flowwithin the internal flow area. The increased time of dilation may allowthe leaflets to undergo viscoelastic creep and create fractures withinthe tissue that allows the flow area for the valve to be greater thanwithout the benefit of a longer inflation time. The increased flow areamay allow for a greater durability for a valvuloplasty procedure.

The benefit of providing for perfusion during a valvuloplasty proceduremay also enable other therapeutic benefits that are not normally viablewith the standard valvuloplasty procedure that only allows ballooninflation for a period of 10-15 seconds. For example, cryoplasty hasbeen very successful for treatment of atherosclerotic disease in theleg. Application of cryo therapy with the balloon assembly presentedherein may allow the valve leaflets to undergo crystalline formationthat can lead to enhanced leaflet fracturing or remodeling that canprovide for potentially greater durability. Cryo fluid can be introducedinto the individual balloons or into the external space to provide thestandard Joule-Kelvin effect that is used in other standard cryosystems. Alternately, application of a restenotic drug to the surface ofthe leaflets may be enabled by allowing the application to occur over alonger period of time.

Ultrasound may also be used with the previously described perfusionballoons. More specifically, an ultrasound transducer or multipletransducers can be located in the external spaces around the perimeterand within the external wrap of the perfusion balloon. Alternatelyultrasound transducers can be located within each of the cylindricalballoons or located in either of the fluid lines in fluid communicationwith the interior of the balloons or the external spaces around theballoons. For example, an axially vibrating sheathed wire can be locatedin the fluid channel that is used to inflate the five distally locatedballoons. The means to vibrate the wire can be located outside of thebody and can be a part of the manifold of the catheter. The vibratingmotion then is transmitted via the wire down the catheter shaft and isseen as a small pressure pulse within the fluid of the balloons thatoccurs very rapidly at a frequency typically used to break up plaque orcalcium; this frequency could be in the ultrasound range. As theperfusion balloon is inflated, the ultrasound energy located in thefluid of the balloons or the external spaces is activated and causes thecalcium within the leaflets to become disrupted resulting in a softerleaflet that tends to remain patent for a longer period of time. Alsothe leaflets can be broken apart along their commissures more completelyresulting in an improved valvuloplasty procedure.

Providing perfusion while undergoing valvuloplasty may require that theballoon assembly be equipped with a temporary valve. Such a valve mayconsist of, for example, two thin plastic sheets attached along theperimeter of the flow area in much the same way that a venous valve isconstructed or it can have a structure similar to a tricuspid valve. Thetemporary valve can function for periods of minutes or hours ifnecessary to ensure that blood that is pumped into the aorta does notregurgitate back into the left ventricle. The temporary valve can beplaced at either the distal end or the proximal end of the central flowarea.

It is further understood that this perfusion balloon assembly can beapplied not only to the aortic region for valvuloplasty, but also hasapplication in the venous system, smaller vessels of the body, and othernon-vascular tubes of the body. For example, the smaller arterialvessels of cardiovascular system including the carotid artery maybenefit from a perfusion balloon. The design of the balloon assembly isessentially the same as that described with a downsizing or upsizing ofthe balloons to match the vessel diameter of interest.

The present invention has been described above with reference tospecific embodiments. However, other embodiments than the abovedescribed are equally possible within the scope of the invention.Different method steps than those described above, performing the methodby hardware or software, may be provided within the scope of theinvention. The different features and steps of the invention may becombined in other combinations than those described. The scope of theinvention is only limited by the appended patent claims.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

1. A medical device comprising: an elongated tubular member having aproximal end connectable to a fluid delivery device and a distal end;and, a balloon disposed on a distal end of said elongated tubular memberand in communication with the fluid delivery device; said balloon havinga distal region formed of a non-compliant material, a middle regionformed of a semi-compliant material and a proximal region formed of anon-compliant material.
 2. The medical device of claim 1, wherein at afirst inflation pressure, a diameter of said middle region is less thana diameter of said distal region or proximal region.
 3. The medicaldevice of claim 2, wherein at a second inflation pressure larger thansaid first inflation pressure, said diameter of said middle regionincreases relative to said diameters of said proximal region and saiddistal region.
 4. The medical device of claim 4, further comprising apressure sensor in communication with an internal lumen of said balloon.5. The medical device of claim 4, further comprising a display arrangedto display a graph of pressure data versus time sensed with saidpressure sensor.
 6. The medical device of claim 5, further comprising acomputer circuit configured to determine an inflection point of saidpressure versus time data.
 7. The medical device of claim 6, whereinsaid computer circuit is further configured to determine an annulus sizebased on said pressure data.
 8. The medical device of claim 3, furthercomprising a support structure that limits the enlargement of saidmiddle region.
 9. The medical device of claim 8, wherein said supportstructure comprises a plurality of braided members bonded to said waist.10. The medical device of claim 1, wherein said middle region comprisesa support structure that restricts its axial length from enlargement asfluid volume is delivered to said balloon.
 11. A medical device fordilating stenotic valve leaflets, comprising: an elongated member sizedfor advancing within the vascular system of a patient; a balloondisposed on a distal end of said elongated member and in communicationwith said lumen of said elongated member; said balloon having a middleregion comprising a semi-compliant material, a first end comprising anon-compliant material; and a second end comprising a non-compliantmaterial; wherein when said balloon is brought to an equilibriumpressure, said middle portion forms a waist having a smaller diameterthan said first end and said second end.
 12. The medical device of claim11, further comprising a pressure system configured to monitor apressure within said balloon and determine a size of said middle portionof said balloon.
 13. The medical device of claim 12, wherein saidpressure system determines said size of said middle portion of saidballoon.
 14. The medical device of claim 13, wherein said pressuresystem monitors said pressure within said balloon for a pressureinflection point and wherein said inflection point indicates contact ofsaid middle region with an annulus of a patient.
 15. The medical deviceof claim 12, wherein said pressure system monitors said middle portionof said balloon for contact with a valve annulus of a patient.
 16. Amedical device for treatment of a patient, comprising: an elongatedmember sized for advancing within the vascular system of a patient; afluid delivery device connected to a lumen of said elongated member; aballoon disposed on a distal end of said elongated member and incommunication with said lumen of said elongated member; said balloonhaving a middle region, a distal region; and a proximal region; and apressure system in communication with said balloon; wherein saidproximal region and said distal region are limited from expansion at afirst inflation pressure and wherein said middle region is unrestrictedfrom expansion at said first inflation pressure; wherein said pressuresystem determines contact with said middle portion and said vasculaturesystem at a pressure higher than said first inflation pressure.
 17. Themedical device of claim 16, wherein said pressure system and said volumesensor send signals to a computer chip that determines contact with saidmiddle portion by detecting a change in a rate of pressure increaseversus volume within said balloon.
 18. The medical device of claim 17,wherein said computer chip determines a diameter of a valve annulus of apatient based on said change in said rate of pressure increase versusrelative volume within said balloon.
 19. The medical device of claim 18,wherein said distal region and said proximal region comprisenon-compliant material and wherein said middle region comprisessemi-compliant material.
 20. The medical device of claim 19, whereinsaid middle region is smaller in diameter than said distal region andsaid proximal region when said balloon is inflated to an equilibriumpressure. 21-53. (canceled)